Recent data on the physiology of pain
Guirimand, F.
Nephrologie 24(7): 401-407
2003
ISSN/ISBN: 0250-4960 PMID: 14650754 Document Number: 555394
Along the time, the relation between a painful stimulus and the created perception keeps on evolving. The distortion between stimulation and perception concerns all the steps of the painful messages transmission, from the peripheral level to the supraspinal sites. At the peripheral level, C or A delta fibres are excited by noxious stimuli. Involved molecules are released from cellular lysis, inflamed surrounding tissues and C or A delta fibres themselves. The progresses of molecular biology have once again enriched this peripheral inflammatory mix, which composition becomes more and more complicated: ATP and P2X3 purinergic receptor, bradykinin and B2 bradykinin receptor, H+ and ASIC proton receptor, vanilloïd receptor activated by heat, inflammation and increase in synthesis of sodic channels resistant to the tetradotoxine (TTXr).... The first synapses are modulated by excitatory amino-acids and many peptides, at the end of the peripheral nerves in the dorsal horn of the spinal cord A lot of supraspinal sites are activated: the brain stem, the pontomesencephalic regions, the thalamic sites and the cortex. Along the way, multiple mechanisms modulate the pain transmission: the painful perception depends on the balance between both exciting and inhibitory effects. Descending inhibitory controls triggered by noxious stimuli would play a decisive role in the extraction of the painful characteristic of information and would give it priority over other stimuli.